#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    int change(int amount, vector<int>& coins) {
        int n = coins.size();
        vector<long long> dp(amount + 1, 0);
        dp[0] = 1;
        for (int i = 1; i <= n; i++)
            for (int j = coins[i - 1]; j <= amount; j++)
                dp[j] += dp[j - coins[i - 1]];
        return dp[amount];
    }
};